In a 4-quart saucepan, bring 3 cups water to a boil and stream in the polenta while whisking constantly. Bring to a boil, then lower to a simmer and cook 20 minutes, stirring regularly. Set aside and cover with plastic wrap.
In a 12-inch saute pan, heat the olive oil over medium-high heat until just smoking. Add garlic and chile and cook until softened, about 30 seconds, being careful not to brown the garlic. Add wine and bring to a boil, then add shrimp and cook until just cooked through. Remove from heat and add butter, lemon juice, and parsley. Season with salt and pepper and set aside.
To plate, place about 1/4 cup of the soft polenta in the center of each plate. Divide the shrimp mixture over top and serve.